The present invention relates generally to multi-element sealing assemblies for effecting a seal between relatively moveable parts in both the static and dynamic mode at both high and low pressures. More particularly, the present invention relates to an improved low pressure seal ring designed for use in such multi-element seals.
Numerous different seal configurations have been designed for providing a seal between relatively reciprocating surfaces, such as pistons and the cylinders housing the pistons, under both high and low pressure conditions. In my prior U.S. Pat. Nos. 4,231,578 and 4,268,045, a number of different multi-element seal assembly embodiments are disclosed. The seal assemblies are designed to provide an effective seal during both high pressure and low pressure conditions. The contents of these two patents are hereby incorporated by reference.
The multi-element seals disclosed in my prior patents generally include a high pressure seal ring and a low pressure seal ring. The high pressure seal ring is typically made from materials such as polytetrafluoroethylene. The low pressure seal ring is typically made from an elastomeric material such as rubber or other suitable synthetic or natural material having the same elastic properties as rubber. Both the high pressure seal ring and the low pressure seal ring are conventionally housed within a groove within one of the reciprocating surfaces. The low pressure ring typically seats against the bottom of the groove, with the high pressure seal ring being located between the low pressure seal ring and the reciprocating surface to be sealed.
The low pressure seal ring is designed to provide a radial biasing force against the high pressure seal ring to insure adequate sealing at high pressures. In addition, the low pressure seal ring includes a seal lip portion or wiper arm which extends out past the end of the high pressure seal to provide direct contact and low pressure sealing between the low pressure seal ring and the reciprocating surface to be sealed.
In my above referenced prior patents, the radial width of the low pressure seal ring is oversized so that the low pressure seal ring provides a compressive force against the high pressure seal ring. The low pressure seal ring is compressed within the seal groove. Additionally, the low pressure seal ring is designed to be over-sized so that a radial compressive force is exerted against the seal lip or wiper arm to thereby promote sealing at low pressures. Although the use of an over-sized low pressure seal ring provides desirable biasing of the seal lip against the reciprocating surface, it was found that the particular over-sized configurations being used resulted in increased friction and excessive wear of the tip portion of the low pressure seal ring lip. Accordingly, it would be desirable to provide a low pressure seal ring which provides adequate biasing of the seal lip against the reciprocating surface to prevent leakage during both high and low pressure operation while reducing wear on the seal lip.